Poor admin for debit orders

I have been asking MTN to switch my debit order date from the 15th to the end of the month for nearly 3 years now. I have been to several stores and called and still my debit orders go off on the 15th instead of the end of the month. I have asked them to change it so many times and i am done begging them to sort their stuff out. Once my contract has elapsed they will never see me again. I will take my business elsewhere.